1.8 Miata cat on a 1.6 car

Question for you Miata nuts. My '91 has a gutted catalytic converter (due to its prior clogging and an imminent need to get it roadworthy). I just found out that Tom has an extra Flyin' Miata high-flow cat sitting around unused. It was the first upgrade done to his 1.8 project car before it got turbo power.

We're thinking of fitting that cat to my car, but I understand there's a difference in flanges. So, what's it take to make the 1.8 cat fit between the 1.6 header flange and stock cat-back? Is it a matter of slotting the bolt holes, or is it more complicated?

The header currently in the car is a Raceland brand one, but it bolts right up to the 1.6 cat. The header outlet pipe measures 2" OD.

if there is any difference its going to be on the flange that bolts to the header. the catback exhausts are interchangable.

Anyone? We might just have to try it and find out.

The difference is in the header flange. It's at a different angle and dramatically smaller. If you had a stock header on the car, I'd say to get the downpipe section of a 1.8 and put a plug in the O2 sensor hole, then it would bolt together. If you had an FM turbo, I'd say to call us up and ask us for the piece that lets a 1.6 car use a 1.8 cat. Since you have an aftermarket header, welders will be involved.

Thanks, Keith.